Hydrochemical Evolution, Anthropogenic Influences, and Irrigation Suitability of Groundwater in the Zhangye Basin, Northwest China

Groundwater is a critical resource in arid regions, requiring careful evaluation of its quality, source origins, and suitability for irrigation. This study assessed groundwater in three Zhangye Basin irrigation districts using Gibbs diagrams, ionic ratios and correlation analyses, and principal component score-multiple linear regression modelling to determine chemical characteristics, source contributions, and irrigation potential. Irrigation suitability was evaluated using sodium adsorption rate (SAR), percentage of sodium content (%Na), permeability index (PI), and residual sodium carbonate (RSC) indices. Findings showed that groundwater across the three irrigation districts is generally mildly alkaline, dominated by Na+ cations and SO₄^2 - anions. Groundwater chemical composition was predominantly controlled by evaporite weathering and leaching, which accounted for 51.25% of total influence, whereas carbonate and silicate rock contributed 18.18%. Anthropogenic activities, predominantly NO₃⁻ , represented 13.32%. Irrigation suitability analysis indicated that most groundwater across the Zhangye Basin was suitable for irrigation use. However, elevated SAR, %Na, and RSC values in certain zones of the Gaotai Irrigation District’s piedmont alluvial plain render those areas unsuitable for irrigation purposes. Overall, findings highlight the dominant geochemical processes shaping groundwater quality and provide guidance for sustainable irrigation management in the Zhangye Basin.